The present invention relates to a method for simultaneously resistance brazing multiple conductor joints and more particularly for the method of simultaneous resistance brazing of adjacent conductor joints in the windings of stators for alternators, generators, and dynamo-electric machines.
It is extremely difficult to perform resistance brazing of adjacent parts which are arranged in multiple rows and columns because of the difficulty in acquiring tooling of the proper size, shape and strength for the electrodes of a resistance welder/brazer within the small spaces that typically exist between such rows and columns particularly in stator windings for electrical alternators, generators and motors.
Because of the costs and difficulty of fabricating stator cores and other windings in electrical generators and alternators using a single continuous wire in the winding process, such windings are typically fabricated from a multiplicity of individual conductor segments or “hairpins” which are preformed and adapted to be placed into slots or grooves in, for example, a stator core. These hairpin conductors must be joined to one another at their end portions to form the stator winding for the dynamo-electric machine. Various prior art methods have been used to join the end portions of the conductors to form the stator winding including soldering, welding, and brazing. For example, U.S. Patent Application No. US2002/0041129A1-Oohashi, et al., published Apr. 11, 2002 demonstrates a number of such techniques. As illustrated in the Oohashi application, the respective end portions of the conductors are brazed by placing a brazing compound between the respective joints and then applying an electrical current through electrodes so that the brazing compound is heated and melted to join the conductors together.
Oohashi also discloses that a technique of brazing multiple joints arranged in rows by placing a brazing compound between the joints to be brazed and then pressing the entire row together between electrodes so that the electrical current flows through the entire row melting the brazing compound and joining the respective conductive joints. For example, as illustrated in FIG. 6 of Oohashi adjacent pairs of contacts are pressed together with the electrodes to form an electrical path for the resistance brazing of the joints. One disadvantage of the method disclosed in Oohashi is that the pressure applied by the electrodes necessary to form an electrical connection through an entire row of electrodes can cause the metal of the conductors to bend or deform so that there is an undesirable electrical contact between adjacent pairs of the conductors which results in improper operation of the stator core. It is important to maintain the proper spacing between adjacent pairs of conductors so that the electrical current does not flow between the respective pairs during operation of the dynamo-electric machine.
Thus, it would be a desirable advance in the art to provide a method of simultaneously brazing multiple pairs of conductor end portions arranged in a row simultaneously without bending or distorting the spacing between the respective pairs of conductor end portions.